This project focuses on the innovative application of statistical methods to analyze data on human illnesses, particularly cancer. Most of our efforts have centered on data from two large national studies: the National Health and Nutrition Examination Survey (NHANES) and the Surveillance, Epidemiology, and End Results (SEER) study. Using data on chest x-rays from the NHANES I (1971-1975) and NHANES II (1976-1980) studies, we estimated the prevalence in the US of pleuroconiosis (i.e., radiographically detectable, dust-related, pleural thickening). Pleuroconiosis is believed to be a specific marker of asbestos exposure, as well as being correlated with excess mortality and increased risk of lung cancer. In the five years between studies, the prevalence estimates for persons aged 35-74 rose from 0.3% to 1.7% for females, 3.2% to 6.4% for males, and 1.6% to 3.9% overall. Some chest films from each of the two studies, which were originally evaluated by different sets of three readers, were re-examined by a single reader. Even though the individual rates from the rereadings are not directly comparable to those from the original studies, the differences between the 1973 and 1978 rates are comparable. For the subset that we re-examined (white males aged 45-74), the rate nearly doubled from 1973 to 1978, which is consistent with the original readings. We also analyzed SEER data from 1975 to 1994 to search for unexplained patterns in cancer incidence in the US. Our analysis focused on long-term time trends in incidence and on deviations from those trends attributable to birth cohorts or to calendar periods. On average, cancer incidence rose 0.8% annually in white women and 1.8% in white men. After taking smoking and increased screening into account, average annual increases fell to 0.1% in white women but persisted at 1.7% in white men. In particular, yearly increases in non-Hodgkin's lymphoma averaged 2.4% in white women and 4.7% in white men. Among men, incidence changes attributable to cohorts grew progressively larger from one cohort to the next. Cancer incidence patterns among black men and women were similar to those among whites despite smaller population sizes.